Telephone system.



IE.'A.GRAHAM.

TELEPHONE SYSTEM. APPLlCATlON FILED MAR. 31, 1914.

1,179,175. x Patented Apr. 11,1916.

3 SHEETS-SHUT I.

TELEPHONE SYSTEM.

APPLICATION FILED MAR. 31. 1914.

1 1 79, 1 75 Patented Aim 11, 1916.

' ,3 SHEETS-SHEET 2- @WM XMQQMM E. A. GRAHAM.

. TELEPHONE SYSTEM.

I APPLICATION FILED MAR! 3 l| [914- Patented Apr. 11, 1916.

3 SHEETS-SHEET 3- 1 E COLUMBIA PLANuGRAPl-x co., WASHINGTON n c EDWARDALFRED GRAHAM, OF BROCKLEY, LONDON, ENGLAND.

TELEPHONE SYSTEM.

To all whom it may concern Be it known that I, EDWARD HAM, a subject ofthe King of Great Britain and Ireland, residing at Brockley, in thecounty of London, England, have invented Improvements in TelephoneSystems, .of which the following is a specification.

This invention relates to telephonic circuits particularly applicable toloud speaking telephones and it includes arrangements wherein the modeof operation is that Well known as the common battery or central energysystem in which the electrical supply circuit includes relatively highimpedances and is in parallel with transmitter and receiver circuits,the increase or decrease of current, consequent upon the variation inthe resistance of the transmitter of one circuit causing a correspondingdecrease or increase in the current through another circuit containing areceiver owing to the effect of the inductance in their common supply.Such circuits have been well known to those versed in the art oftelephony, and early systems of this kind are disclosed in Stones UnitedStates specifications Nos. 5076%, and 508255, Hayes United Statesspecification 474323 and McBertys United States specification 584393 andmany others.

In the specifications particularly referred to, two conductors betweenstations are provided and the transmitters and receivers are connectedin series or in parallel across the two lines. Circuits employing threeconductors with two corresponding parallel circuits each including onlyone transmitter and a receiver or receivers, these circuits beingcompleted by a common return, are a simple modification of the foregoingarrangement and reference may be made to Mix and Genests German PatentsNos. 15287 2 of 190% and 159780 of 1905, wherein the transmitter of oneinstrument is in parallel with the receiver of another instrument andvice versa and the two circuits thus arranged are bridged by theelectrical supply apparatus which includes inductance coils. No claimtherefore is made in'the present specification for the method ofconnecting telephonic elements as hereinbefore mentioned.

The principal feature of the present invention lies in the arrangementof the inductance coils which, in this case, form a part of thetelephone instruments proper and which are so arranged that the currentSpecification of Letters Patent.

ALFRED ,GRA-

Patented Apr. 11, 1916.

Application filed March 31, 1914. Serial No. 828,552. y

for supplying the transmitter at the calling station flows through thewinding of the inperform functions other than those purely vtelephonic,for instance it may serve as the energizing coil of a relay acting forvarious purposes, or as a magnetizing or polarizing coil of thereceiver. Flgures 1 to 12 of the accompanying drawmgs are dlagrams eachillustrative of a station arrangement in accordance with the inventionIn F1g. 1 A is an inductance coil placed mthe posltive supply line 39which, although example when machine generated current is used, is notessential to the operation of the system. B and B are-inductance coils,situated in the telephone apparatus and acting for other purposes ashereaftermentioned, C and C are condensers or the like, D and D are thetelephonic receivers, E and E are transmitters and F and F areinterrupters or vibrators of the kind which, when functioning, cause ahooting noise to be emitted from the receiver of the distant station,for calling attention. G and G are switch arms adapted respectively tobe placed in connection with contactsH andI and H and P. J, K, L, and Mindicate line wires connecting the two instruments. When communicationis required, say from station X to station Y, the switch arm G is causedto vpress against contact 1. Current will then flowfrom the positivesupply lead 79 through the windings of the inductance coil B at stationY along the line L, through the interrupter F, and contacts I, Gatstation X and along the line K to the negative supply lead 7; Thereceiver D at station Y with the condenser C is in shunt to the, saidcircuit containing the interrupter, and current fluctuations,alternating in character, consequent upon the operation of theinteradvantageous in some circumstances, as for I rupter, will flowthrough the receiver winding D and cause the receiver to emit a loudhoot or call. F or a voice call, the switch arm G is caused to engagecontact H where by current is caused to flow from the positive supplylead 12 through the inductance coil B at station Y, along line L,through transmitter E and contacts G H and along conductor K to thenegative supply lead 1". Upon the transmitter E functioning, a varyingcurrent will pass through the condenser (l and the windings of thereceiver D causing emission of speech therefrom. The same series ofoperations applies for calling from station Y to station X and, ofcourse, in this case the feeding current for the interrupter F andtransmitter E flows through the windings of the inductance coil 13 atstation X.

As the feeding currents for the calling device and transmitter at thecalling station flow through the windings of the inductance coil locatedat the called station, it will be understood that by suitableconstruction the inductance coils may be adapted to perform variousfunctions other than that particularly telephonic. Thus in Fig. 2, theinductance coil B is shown as provided with an armature N having asuitable flag 0 attached thereto so that upon current flowing, the coiland its core becoming magnetized, the armature N will be attracted andthe flag moved into such position behind a window 0 as to give a visualsignal of the fact of a call being made to that particular telephoneinstrument, as is necessary when a number of telephones are mounted inclose proX imity.

Fig. 8 shows the arrangement of a telephone station in which theinductance coil B is provided with an armature N as in the previouscase, but the actuation of the armature serves to close a local circuita at the contact bafter the manner of a relay and thereby causes asignal lamp P to glow, affording an indication of a call. Q, is aplunger which may be actuated from without the telephone casing to closethe local circuit through the signal lamp P by hand. This arrangementgives a ready indication as to the condition of the supply circuitwhich, if complete, and the signal lamp P without fault, will cause thelatter to glow, thus obviating the necessity of opening up theinstrument for testing, or of receiving a call from a distant positionas would otherwise be required when testing the circuit. As current foroperating the interrupter F or F at one station flows through theinductance coil B or B at the other station, it can be ascertained thatthe circuit is complete at the called station by causing the interrupterto function, the buzz being audible locally c. 6., at the callingstation. It is therefore possible to test the continuity of the supplyleads at both ends from one station only.

In connection with telephone apparatus in which calls by interrupter orvoice are provided for, it is occasionally necessary to employ loudringing call bells and in Fig. 4 such an arrangement is indicated. Uponthe circuit at the distant station being com.- pleted the inductancecoil B becomes encrgized and the armature N is attracted, therebycompleting a local circuit it, including the call bell R, from thepositive lead p to the negative lead 1' through the contact 5 and acontact S with which the switch arm G is normally in engagement. Whenthe switch arm G is placed in connection with the contact H for thepurpose of completing the transmitter circuit, the arm G leaves thecontact S and opens the local circuit a so that the call bell R will notring during conversation. This figure illustrates also the applicationof the inductance coil for a purpose additional to'that of a relay wherea part B of the windings of the inductance coil (the remainder beingshown at B) is employed to form an energizing coil for the receiver 1)and used in lieu of a permanent magnet such as is usually embodied inreceiver construction.

In a modified arrangement the interru'pter F or F at each station may beomitted and in this case it is only necessary to complete thetransmitter circuit, as for speaking, to cause the call bell to ring.Such an arrangement is shown in Fig. 5 where the local circuit n isarranged to be closed by way of the contacts Z) and I. llf for example acall is being made from station X to station Y, then the switch arm G iscaused to engage contact H whereupon current will flow from the positivelead through the inductance coil B along line L through the transmitterE, contact H, arm G and along line K to the negative lead 7'. Thearmature N of the'coil B at station Y is in consequence actuated andcompletes through the contacts 72 and I the local circuit n includingthe signal bell R. Upon station Y replying, the local circuit n isbroken by the switch arm G leaving the contact I and the speakingcircuit is then completed through contact H As an alternative tobreaking the local bell circuits a, n by movement of the switch arm G orG as described, non-inductive relays T, T may be introduced into thetransmitter circuits as shown in Fig. 6 and the bell circuits brokenthereby. In this case-supposing station X to be calling station Y-uponthe switch arm G being engaged with contact H, current flows from thepositive supply lead 7 through coil B, along line L, through the windingof relay T, transmitter E and along line K to the negative supply leadr. The armature N at station Y being thus attracted the local circuit aincluding the call bell R is completed through the contacts 12 and V andthe armature U of the local non-inductive relay T that is arranged to beplaced in the corresponding transmitter circuit at station Y. l/Vhen thetransmitter circuit at station Y is completed ready for reply thecurrent flowing through the Winding of the noninductive relay T willcause attraction of the armature U which will leave the contact V and sobreak the local bell circuit a whereupon uninterrupted conversation cantake place. Call bells are referred to as being included in the localcircuit, but other alarm or signal devices of known kinds may of coursebe employed.

It is sometimes desirable that a called station shall be able to replywithout the necessity of manually completing the local transmittercircuit at such called station. may be effected according to the presentinvention by connecting, at say station X, the transmitter E to thearmature N, as shown in Fig. 7. Upon completion of the transmittercircuit at the distant station Y for.

calling station X, current will flow through the windings of theinductance coil B at the latter station and the armature Nwill-consequently be attracted and connect the line J, carrying feedingcurrent, to the transmitter, by which means the reply circuit iscompleted and so remains until the transmitter circuit at the distantstation is broken.

Other modifications of circuits such as described are shown in Figs. 8,9 and 10. In Fig. 8 local sources of electrical energy, as for instancebatteries IV, are employed in which case it is only necessary to providethree conductors between the instruments. Otherwise the circuits are asdescribed with reference to Fig. 1. In Fig. 9 the connections of thetelephone stations are as shown in Fig. l the external wiring beingmodified only to the extent which will be readily understood withoutfurther description; the positive and negative supply lines 79 and 7'which may form a ring main, being common to any number of telephoneinstruments. In Fig. 10 the connections of the telephonic elements inthe instruments are so modified as to require the employment of but oneline wire L in addition to the positive and negative supply leads K M.In this case when either of the transmitter circuits is completed,current flows through the inductance coils B, B at both the calling andcalled stations. Thus when the switch arm G at station X bears oncontact H current flows to the transmitter E by two paths, one directthrough the inductance coil B and the other through the inductance coilB and the line wire L IVith the transmitter E in operation, alternatingThis forth. As an example, the circuit of a bell may be closed by theuse of the inductance coil B and broken during conversation, as

before, by the movement of the transmitter switch G As an illustrationofthe application of the inductance coil for a purpose other than that ofa relay and for a purely telephonic function, Fig. 11 may be referredto. The arrangement of the other elements of thecircuit'in this figureis as previously described but a part B ofthe windings of the inductancecoil (the remainder being shown atB) is, in the figure, employed to forman energizing coil for the receiver D as in Fig. 4: and used in lieu ofa permanent magnetsuoh as is usually embodied in receiver construction.The whole of the inductive windings may, if desired, take the form ofenergizing coils for the telephone receivers.

In Fig. 12,- the telephone station connections are modified by theintroduction of a repeater coil Z as frequently used in telephonesystems, but otherwise the arrangement and operation is as hereinbeforedescribed. It will be understood that when such a repeater coil isemployed the inductance coil B, may be omitted as such repeater coilwould be available for use as a relay or for the other purposes referredto in describing the inductance coil.

As will be obvious, the invention herein disclosed can be carried out inother Ways than those specifically described, without departing'from theessential features thereof which more particularly relate to theemployment of telephonic inductance or like coils located at telephonicstations and so arranged that current flows through the windings of thesaid coil or coils located at the called station when the electriccircuit is completed at the calling station, the said coils beingtherefore available for service other than the purely telephonicfunction of causing reproduction of speech and prevent ing crossspeaking or overhearing.

Although pairs of telephones only are shown in communication in thedrawings it will be obvious that the systems indicated may be applied toexchange working or to systems of communication between a controlposition and several sub-positions.

What I claim is 1. A telephone system comprising at one stationa'series-connected receiver and condenser and at another stationv atransmitter and a current interrupter, leads and switching means adaptedto connect the transmitter and interrupter alternatively to the saidreceiver, a source of current supplying such leads and a windingpossessing inductance associated with the receiver for polarizing thesame, such winding carrying the supply current for the transmitter.

2. A telephone system comprising at one station a series-connectedreceiver and con denser and at another station a transmitter and acurrent interrupter, leads and switching means adapted to connect thetransmitter and interrupter alternatively to the said receiver, a sourceof current supplying such leads, a winding possessing inductanceassociated with the receiver for polarizing the same, such windingcarrying the supply current for the transmitter, and indicating meansoperated by the winding when the latter is excited.

3. A telephone system comprising at one station a series-connectedreceiver and con denser and at another station a transmitter and acurrent interrupter, leads and switching means adapted to connect thetransmitter and interrupter alternatively to the said receiver, a sourceof current supplying such leads, a winding possessing, inductanceassociated with the receiver for polarizing the same, such windingcarrying the supply current for the transmitter, a switching memberadapted to be operated by said winding when energized, a local circuitadapted to be closed by such switch member and an indicating deviceincluded in said circuit.

4;. A telephone system comprising at one station a series-connectedreceiver and con denser and at another station a transmitter and acurrent interrupter, leads and switching means adapted to connect thetransmitter and interrupter alternatively to the said receiver, a sourceof current supplying such leads, a winding possessing inductanceassociated with the receiver for polarizing the same, such windingcarrying the supply current for the transmitter, a switching memberadapted to be operated by said winding when energized, a local circuitadapted to be closed by such switch member, an indicating deviceincluded in said circuit and means for opening such local circuit duringconversation.

5. In a telephone system, two instruments each comprising aseries-connected receiver and condenser, a transmitter and aconversation switch, a source of current, leads con necting theinstruments together and to such source of current, a winding possessinginductance associated with each receiver, the winding at one instrumentcarrying the sup ply current from the transmitter of the otherinstrument when the conversation switch at the latter is closed, amovable switch member associated with each inductance winding and acorresponding local. circuit adapted to be closed when the conversationswitch originating a call is closed for calling and to be opened uponclosure of the said conversation switch for conversation.

6. In a telephone system, two instruments each comprising aseries-connected receiver and condenser, a transmitter, a currentinterrupter and a switch adapted to alternatively connect thetransmitter and interrupter in circuit, a source of current, leadsconnecting the instruments together and to such source or" current, awinding possessing inductance associated with each receiver, the windingat the calling instrument carrying the supply current for thetransmitter or interrupter of the other instrument depending upon theoperation of the switch at the calling instrument, a movable switchmember associated with each inductance winning and a corresponding localcircuit adapted to be closed when the switch originating a call isclosed and to be opened with closure of the switch to close thetransmitter circuit.

7. In a telephone system, two instruments each comprising a seriesconnected receiver winding, a condenser and an inductance winding, atransmitter and a switch device, a line wire connecting the receiverwindings together, a line wire connecting one terminal of thetransmitter of one instrument to a point between the inductance windingand condenser of the other instrument said switch device being adaptedto connect the other terminal of the transmitter to the first mentionedline wire and a source of current having one pole connected to theinductance windings and the other pole to first mentioned line wire.

8. In a telephone system, two instruments each comprising aseries-connected receiver winding, a condenser and an inductancewinding, a transmitter and a switch device, a line wire connecting thereceiver winnings together, a line wire connecting one terminal of thetransmitter of one instrument to a point between the inductance windingand condenser of the other instrument said switch device being adaptedto connect the other terminal of the transmitter to the first mentionedline wire, a. source of current having one pole connected to theinductancewindings and the other pole to first mentioned line wire, alocal circuit including a signaling device at each instrument adaptednormally to be connected to one pole of the source of current and aswitch member adapted to be operated by the correspond ing inductancewinding when energized and to connect the other end of said localcircuit to the other pole of the source of current.

9. In a telephonic system, two instruinterrupter alternatively to thefirst mentioned line wire and a source of current having one poleconnected to one end of the inductance windings and its other poleconnected to the opposite end of the receiver windings.

10. In a telephonic system, two instruments each comprising a seriesconnected receiver winding, a condenser and an inductance winding, atransmitter and a switch device, a line wire connecting the receiverwindings together, a line wire connecting one terminal of thetransmitter and one terminal of the current interrupter in oneinstrument to a point between the inductance winding and condenser inthe other instrument, said switch device being adapted to connect theother terminals of said transmitter and current interrupteralternatively to the first mentioned line wire, a source of currenthaving one pole connected to one end of the inductance windings and itsother pole connected to the opposite end of the receiver windings, alocal circuit including a signaling device one terminal of which isarranged normally to be connected to one pole of said source of currentby said switch device and a second switch device adapted to connect theother terminal of said local circuit to the other pole of said source ofcurrent each inductance winding having one part thereof arranged topolarize the corresponding receiver and another part to automaticallyclose the second switch device.

Signed at London this tenth day of March, 1914.

- EDWVARD ALFRED GRAHAM.

Witnesses: I

EDWARD E. BARNARD HENRY WM. DIPROsE.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents,

Washington, D. 0." i

